1. Field of the Invention
The present invention relates to a tool for tightening and melt-adhering a strap. More particularly, the invention relates to a tool for tightening and melt-adhering a strap, which is light in weight, markedly improves the operation efficiency as a result of omitting manual operation, and is equipped with a timing mechanism which can be easily adjusted to determine an expected friction time for establishing a suitable melt-adhering condition for the strap.
2. Prior Art
There have heretofore been proposed a variety kinds of tools with which a strap made of a thermoplastic material such as polypropylene (PP), polyethylene terephthalate (PET) or polyamide resin is wound round a package thereby to form a loose strap which is then tightened by a knurled roller to form a tight strap, and the overlapped portion of the strap is rubbed under the application of a pressure, and these tools have already been placed in the market. Among them, the newest model has been disclosed in, for example, Japanese Examined Patent Publication (Kokoku) No. 29644/1995 (U.S. Pat. No. 5,169,480) filed by Signode Corporation. In order to reduce the weight, this tool has only one hydraulic pressure motor which is used for tightening a loose strap and for driving a vibrator for rubbing the overlapped portion of the strap, by mechanically changing over the hydraulic pressure motor by using a manual lever, a cam and a clutch.
According to this tool, however, the pressure of the knurled roller or the vibrator is exerted on the overlapped portion of the strap and the unnecessary part of the strap is cut by hand using the manual lever. Therefore, the tool must be operated by both hands, causing the operation efficiency to become poor, causing the worker to be tired with, and making it difficult to continue the operation for extended periods of time.
The above-mentioned Japanese Examined Patent Publication (Kokoku) No. 29644/1995 incorporates a fluid (pneumatic)-type timing mechanism for limiting the rubbing time disclosed in Japanese Examined Patent Publications (Kokoku) Nos. 45360/1969 and 46880/1974, and U.S. Pat. No. 3,654,033 previously filed by the applicant of the present application, and seems to be achieving the effects correspondingly involving, however, such problems as narrow range for controlling the friction time and difficulty in the control operation due to the structure.
In order to improve these problems, therefore, the present inventors have forwarded the study concerning a cylinder for pressurizing a tightening roller and for turning the tightening roller back and forth, and have further employed a fluid pressure motor exclusively for a vibrator and improved the timing mechanism while paying effort so will not to increase the weight, and have arrived at a tool which is very easy to handle as contemplated by the present invention.
The object of the present invention is to provide a tool for tightening and melt-adhering a strap, which is light in weight, easy to operate, causes the worker to be less tired with, and enables the operation to be continued for extended periods of time.
Another object of the present invention is to provide a tool for tightening and melt-adhering a strap, which cuts the unnecessary part of the strap after it has been tightened, and frictionally melt-adheres the overlapped portion of the strap with the application of pressure relying on the fluid pressure operation minimizing the manual operation, and further enables the tool to be easily separated from the strap after it has been tightened.
A further object of the present invention is to provide a tool for tightening and melt-adhering a strap, equipped with a timing mechanism which makes it easy to adjust the time for rubbing the overlapped portion of the strap over a wide range.
According to the present invention, there are provided:
A tool for tightening and melt-adhering a strap, with which a loose strap wound round a package is tightened by a tightening roller arranged at the overlapped portion of the strap to form a tight strap, an extra strap is cut and removed by a cutter, and a frictional force is imparted to the overlapped portion of the strap to melt-adhere the strap, wherein provision is made of a hydraulic pressure cylinder for pressurizing the tightening roller, a first fluid pressure motor for turning said roller forward and reverse, a fluid pressure cylinder for pressurizing a vibrator that gives a frictional force to the overlapped portion of the strap, and a second fluid pressure motor for driving said vibrator (claim 1);
A tool for tightening and melt-adhering a strap according to claim 1, wherein provision is made of a timing mechanism capable of adjusting the time for feeding a pressurized fluid to the second fluid pressure motor (claim 2);
A tool for tightening and melt-adhering a strap according to claim 2, wherein the timing mechanism works based on a fluid pressure (claim 3);
A tool for tightening and melt-adhering a strap according to claim 3, wherein the fluid pressure timing mechanism is the one of a variable back pressure type, the one of a variable volume type, or the one of a variable back pressure/volume type based on the combination of the two (claim 4);
A tool for tightening and melt-adhering a strap according to claim 4, wherein the fluid pressure timing mechanism is the one of the variable back pressure type in which at least one of the fluid accumulation chambers branched from a main pressurized fluid circuit has a variable back pressure valve for releasing the fluid back pressure, said fluid pressure timing mechanism being further equipped with a shut-off valve which shuts off the main pressurized fluid circuit to the second fluid pressure motor relying upon a fluid pressure stored in the fluid accumulation chamber (claim 5); and
A tool for tightening and melt-adhering a strap according to claim 4, wherein the fluid pressure timing mechanism is the one of the variable volume type in which at least one of the fluid accumulation chambers branched from a main pressurized fluid circuit is of the variable volume type being constituted by a piston that can be moved by a screw directly driven from the external side and a cylindrical fluid accumulation chamber, said fluid pressure timing mechanism being further equipped with a shut-off valve which shuts off the main pressurized fluid circuit to the second fluid pressure motor relying upon a fluid pressure stored in the fluid accumulation chamber (claim 6).